(a) Field of the Invention
The present invention relates to a throttle valve control system for internal combustion engines and, more particularly, to an improved throttle valve control system for an Intelligent Speed Adaptation (ISA) system.
(b) Description of the Related Art
In recent years, much research and development have taken place regarding the concept of intelligent speed adaptation (ISA). Such a system is based on control of the throttle valve to restrict the injection of fuel into the engine when the vehicle reaches specific speed limit.
A conventional throttle valve control device for controlling fuel injection is shown in FIG. 4. Reference numeral 2 in the drawing indicates the throttle valve control device.
The throttle valve control device 2 is provided in a throttle body 4. The throttle valve control device 2 comprises a throttle valve 6, a rotational throttle shaft 8 for actuating the throttle valve 6, a first rotational plate 14 fixedly mounted at one end of the throttle shaft 8 and connected to an accelerator pedal 10 by an accelerator cable 12, and a second rotational plate 22 fixedly mounted at the other end of the throttle shaft 8 and connected to a motor 18 via a throttle cable 20.
The throttle valve control device 2 has two sources of operation, driver manipulation of the accelerator pedal 10 which operates the acceleration cable 12 then the first rotational plate 14, and the motor 18 which is controlled by an ECU 16 and operates the throttle cable 20 and the second rotational plate 22. Accordingly, the throttle valve control device 2 is operated in 3 operational modes: a manual mode, an automatic, and a dual mode.
In the manual mode, the throttle valve 6 is controlled by driver manipulation of the accelerator pedal 10. In this case, the depressing force applied by the driver on the accelerator pedal 10 is transmitted to the throttle shaft 8 via the acceleration cable 12 and the first rotational plate 14. That is, the first rotational plate 14 rotates in one direction in direct proportion to the degree to which the accelerator pedal 10 is depressed by the driver, and rotates in the other direction as the driver releases the depressing force on. At this time, although the motor 18 is connected to the second rotational plate 22, the motor 18 does not affect accelerator pedal manipulation because the ECU 16 does not supply electricity to the motor 18 in the manual mode.
In the automatic mode, the throttle valve 6 is actuated by the motor 18 by control of the ECU 16. In more detail, if the ECU 16 determines that the driver is not performing manual control of the throttle valve 6, the ECU 16 operates the motor 18 by supplying electricity thereto according to a driving state of the vehicle determined on the basis of the data detected by various sensors on the vehicle. In this case, the rotational force of the motor 18 is transmitted to the throttle shaft 8 via the throttle cable 20 and the second rotational plate 22. In the automatic mode, because the first rotational plate 12 is also fixedly connected to the throttle shaft 8, the accelerator pedal 10 moves without driver manipulation of the same in accordance with the rotation of the throttle shaft 8 in the automatic mode,
In the dual mode, the throttle valve 6 can be controlled by both driver manipulation of the accelerator pedal 10 and the ECU 16. That is, a counterforce to the acceleration pedal 10 is given whenever the driver tries to depress the accelerator pedal 10 beyond a predetermined level (i.e., beyond a level which would driver the vehicle past a specific speed limit). However, in the dual mode, since driver manipulation of the accelerator pedal 10 ultimately has priority over automatic control of the throttle valve 6, it is not possible to control vehicle speed electrically if the driver continues to operate the accelerator pedal 10.